This invention relates in general to apparata designed to dispense chemicals at a remote location. More specifically, the present invention relates to apparata which mix two or more chemicals in desired proportions and then control the dispensing of the resultant mixture. Chemical-blending and dispensing apparata, while old in the art, generally fall into one of two design styles or categories. The first category includes those apparata wherein the metering of chemicals to be mixed together is governed by the extent or degree that a control valve is opened. A conventional water faucet is representative of this type of control valve. One drawback with this type of device is the inherent inaccuracy in volume control. Typically, the degrees of rotation of the knob do not accurately correlate to the volume flow rate. Another drawback involves the limitations on automatic ways to open and close the control valve and to control the extent or degree that the valve is opened.
The drawbacks associated with this first category of apparata are solved to some extent by the apparata of the second category. This second category includes those apparata which meter the chemicals to be mixed by electrical solenoid valves (or related devices). These types of valves are either fully opened or completely closed and the volume which flows through this valve is controlled solely by the length of time the valve remains open and the cross-sectional area of the valve passageway. Since the valves are either in an open or closed state, there are no intermediate settings to be concerned with. Since solenoid valves respond to electrical signals, their operation is fast, accurate and easily controlled. By the use of computers, microprocessors and related programming means, a large number of valves can be controlled and their operation managed in virtually an infinite number of ways and sequences. This type or category of device may be found in automated, chemical processing facilities wherein computers manage predominant portions of the production cycle.
Listed below are certain patent references which pertain to chemical-blending and dispensing devices. While each disclosed device may include certain novel aspects, none are believed anticipatory of the claimed invention.
______________________________________ Patent No. Patentee Issue Date ______________________________________ 3,712,513 Ashmead et al. 1/23/73 3,451,402 Howard 6/24/69 4,162,689 Zdrodowski 7/31/79 1,560,044 Derrick 11/03/25 3,823,727 Fry 7/16/74 4,004,884 Zdrodowski 1/25/77 ______________________________________
Ashmead et al. discloses an apparatus and method for gradient elution involving two separate supply sources of chemicals and means to proportion each chemical into a particular mixture. The introduction of each chemical into a mixing chamber is controlled by solenoid valves whose operation is controlled by electronic programming circuitry. The apparatus produces a supply of eluent having a precisely controlled time-varying concentration of each chemical.
Howard discloses a method of continuously blending a gasoline by operating a first engine on a target field and operating a second engine on a sample of the blended gasoline. The knock intensities of the target and sample fuels are compared to generate an error signal, and the error signal provides a basis for adjusting the relative portions of the components forming the blended gasoline. The apparatus employed includes time-controlled valves for introducing blending stocks A and B into a preliminary blending tank. The contents of this blending tank are then pumped to a final blending zone and from there to test engines.
Zdrodowski ('689) discloses a method for accurately controlling fluid flow rates utilizing time division control of pulse valves. The invention is particularly intended for controlling relatively low fluid flow rates such as 60 milliliters per hour or less. A pulse generator governs the control of three pulse valves, each of which corresponds to a different fluid reservoir. A gas line introduced into the top of each reservoir is used to evacuate the reservoirs of the various fluids when the pulse valves are opened.
Derrick discloses a liquid supply system including a pump, and a suction conduit extending from the pump to a source of supply. Also included is a discharge conduit leading from the pump to a remotely located faucet for discharge of the contents of the source of supply.
Fry discloses a foam cleaning system and a foam cleaner including control means actuated by build up of static pressure in a foaming chamber. This buildup of static pressure results in a cut-off of air pressure to the chamber thereby insuring that during periods when foam is not being produced, the pressure on the foamer hose is minimized.
Zdrodowski ('884) discloses a system for metering a plurality of fluids wherein time division switching of flow valves is used in order to provide accurate metering of a plurality of fluids from individual reservoirs. Gas lines connected to the top end of each fluid reservoir assist in evacuating those fluids from the reservoirs when the flow valves are opened.
Although time-controlled metering via solenoid valves is known in the art and frequently employed in devices, there are a number of drawbacks. For example, the accuracy of the device depends upon the timer means employed, the reliability of the solenoid valves and the likelihood of component failures. These concerns are compounded by the fact that devices of this type are somewhat complex and may necessitate a comparatively large number of component parts for each chemical involved. While it is conceded that some timed controlled metering or dispersal of solution may not be able to be avoided entirely, it is believed beneficial to reduce the number of such time-controlled valves to the extent possible and the utility and desirability of a product is enhanced by the minimizing of such components.
The present invention represents a significant improvement over the prior art devices by providing a chemical-mixing and dispensing apparatus which is completely operable without the use of any timed, electrically-actuatable valves as part of the mixing of the various chemicals or solutions involved. Although some valve is desirable to control the delivery of the mixed chemicals to a remote-use location, the remainder of the apparatus operates solely on pressure differentials thereby performing a controlled blending without the expense and uncertainty of electrically controllable solenoid valves or other timed metering means.